Understanding Embryo Aging for IPs
Your surrogate is already “pregnant” before the embryo transfer even happens. It can seem impossible to comprehend, but it is the reality of IVF pregnancies. In a traditional pregnancy, gestational age is determined based on the day of ovulation. Fertilization and implantation of the embryo typically occur roughly two weeks later.
In the case of IVF, and specifically gestational surrogacy, pregnancy works a bit differently. The eggs that will eventually become embryos are not allowed to travel from the ovary into the uterus to await fertilization. Instead, they are removed, either from an intended mother or from an egg donor, directly from the ovary before they are released. This typically happens two weeks into a woman’s typical 28 day menstrual cycle.
Those eggs are then fertilized outside of the body and allowed the begin growing. A reproductive endocrinologist closely monitors the cell multiplication over the next several days. In the case of a planned fresh embryo transfer the eggs will then be transferred into an awaiting uterus on either day 3, 5, or 6 of external development. In the case of a planned frozen embryo transfer the embryos are typically frozen, thawed, and transferred on day 5 of development.
In the meantime, the surrogate or intended mother will be on a hormone therapy regimen that will cause her body to mirror, or mock, where it would be in an unmedicated cycle. This process allows doctors to create the ideal environment for the embryos to implant and grow before moving forward with the transfer.
With this in mind, a woman walks into the fertility clinic on transfer day 2 weeks “pregnant” before the transfer even occurs. During the transfer, the doctor will migrate the embryo or embryos into the awaiting uterus. At the conclusion of the transfer the woman is said to be 2 weeks plus the age of the embryo pregnant. If a 5 day blastocyst was transferred, the woman will walk out of the clinic 2 week and 5 days pregnant.
Of course the term “pregnant” is relative to if the embryos actually implant and continue to develop, an answer that can’t be provided until the Beta is completed in roughly two weeks. At the time of that test, if the result is positive, your surrogate will be somewhere between 4 weeks 3 days, and 5 weeks pregnant.